Air-conditioning apparatus for drying-kilns



H. N; ANDREWS AND R.' M. HOLMES. AIR CONDITIONING APPARATUS FOR DRYING KILNS. APPLICATION FILED MAY 2, 19 18- x 1,343 894 Patented June 22,1920.

"- i Q i F W Harm-y f2. flrzarewS 4 15mg "16' E03 772. Holmes UNITED STATES PATENT OFFICE.

HERVEY N. ANDREWS AND ROY M. HOLMES, OF SOUTH BEND, INIJIANA.

AIR-CONDITIQNING APPARATUS FOR DRYING-KILNS.

Specification of Letters Patent. Patented J 22 1920 Application filed. May 2, 1918. Serial No. 232,084.

To all whom it may concern:

Be it known that We, HERVEY N. AN- DREWS and ROY M. HOLMES, citizens of the United} States, residing at South Bend, in 5 the countyof St. Joseph and State of Indiana, have invented certain new and useful Improvements in Air-Conditioning Apparatus for Drying-Kilns, of which the following is a specification.

This invention relates to an improvement in drying kilns, houses, or rooms, wherein automatic humidity control is provided for the drying agent.

In kiln drying, particularly of lumber,

l5 temperature, circulation, and humidity, in

proper proportion, are essential to drying, and while temperature and circulation have been heretofore directly and relatively controlled, no direet and relative control of the 2 humidity has been heretofore proposed.

Such humidity control devices as have been heretofore used, have been set for a maximum and minimum degree of humidity, and

the regulating devices controlled at such 25 maximum and mlnimum. degree points.-

This permits a variation which is rather detrimental to a proper drying operation, and is in no sense a humidity control.

The present invention contemplates. a

system which is automatically responsive to any and all sources of humidity entering into the drying operation, and maintains, with a slight variation, a predetermined percentage of relative humidity independently 85 of maximum and minimum limits.

In the system of the present invention, steam jet lines are arranged to cooperate with the usual heating coils to supply moisture to build up the relative humidity, and. condensing coils, for the circulation of cold water, are arranged to remove the. moistufe from the circulating heating medium. Valves are arranged to control-the. steamjet feed and the water to the condensing 46 coils. A hygrometer control is arranged to lowing specification, reference being had to the accompanying drawin in which:

Figure 1 is a sectiona view, partlyin elevation illustratingthe improved system.

section of the hygrometer control.

7 such agent.

Fig. 2 is a view in elevation, partly in The invention is here shown as embodying a compartment, designed to indicate any klln, house, or room-. for drying material. The compartment 1, has the usual floor 2, preferably as spaced stringers, on which are laid rails 3, if such are desired. The usual partitions 4 are arranged adjacent the walls of the compartment, forming down fines for the necessary circulation.

In its specific embodiment, the invention includes condensing coils 5, arranged in the down flues, and in any preferred order, the coils receiving water from a common supply through a pipe 6, and discharging through a common outlet, as a pipe 8., In addition to the usual heating coils 7, which may be of any desired construction, the invention contemplates the use ofsteam jets '9, arranged below the floor 2, and adapted to jet steam into the surrounding air when it is desired to increase the humidity. The particular arrangement and construction of these steam jets is immaterial for .the purposes of the present invention, the intention being that, as. with the condensing coils, such jets will be arranged and located with particular regard to the nature of the compartment and material to be dried.

Essentially however, the steam jets should 'be supplied from a common source, as

able valve, will serve the purpose, isarranged to control thedelivery of the steam toall'the jets9, while an appropriate valve 12 is adapted to control the discharge pipe from all the condensing coils, so that through these valves the steam may be out off, and the flow of the condensing gnedium,

as cold water, through the coils prevented. The introduction of the steam from the jets will increase the humidity of the drying agent, while the effective operation of the" condensing coils will take the moisture from controlled wit accuracy, the percentage of iiutigididity of the drying agent may be regu:

If then there is provlded a means wherebi the valves 11 and 12 may be.

The control means is here shown as a r h meter, so that the degree of humidity 0 he drying agent is the control element,

Therefore, the relative percentage of humidity in the drying agent is directly controlled by the humidity present. -The hy grometer, as seen in Fig. 2, comprises a case 13, open to the drying agent, in which, on a post 14 is mounted a combined indicator and switch arm 15, the movement of the arm being balanced by a weight 16. The free end of the arm plays over a segment strip 17, marked, as in degrees, and said arm has secured thereto, slightly beyond the pivot, one end of a hygrostatic element 18, as human hair, the other end of which is secured to a post 19, secured in the case. The element 18, responding to the moisture content of the heating agent, will compel a corresponding movement of the free end of the arm, and this movement is utilized as a means for operating the valves 11 and 12, hereinbefore referred to.

The valve operating means comprises a' to each other and in opposite directions be-' yond the solenoid, so that by the arrangement described, the; action of the solenoid will actuate both valves simultaneously, but oppositely, that is when opening one it will close the other. i

The hygrometer previously described is designed to control the solenoid, and while any deslred means may accomplish this result, it is preferred to provide a relay 27,

which governs the solenoid circuit, here shown as ordinary lighting service mains 28. The action of the relay is governed through a local circuit, including conductors 2i33a1nd 30, having a battery in circuit, as a The terminals of the local circuit lead to the hygrometer, one terminal connected to the post pivotally supporting the switch arm 15, so that the arm is in circuit. The other terminal of the local circuit leads to the indicator strip 17, so that this stripv is in circuit. A slide 32 is adjustable on the strip 17, and is formed so that it may be positioned on the strip above or below the free end of the arm 15, or two such strips may be employed, if desired.

As the free end of the arm 15 does not contact with the strip 17, it is apparent that erate the valves 11 and 12. If therefore, the slide 32 is set at any particular point, the moisture content below such point, the other parts being adjusted accordingly, will operate the valves 11 and 1.2.

To set the structure to maintain a constant relative humidity, say fifty per cent., the slide 32 is set at the 50 on the scale strip. If the humidity is lower the arm 15 closes the local circuit, the valve 11 is opened and the valve 12 is closed. The condensation stops and the steam jets add to the humidity of the air until the local circuit is broken, when the parts are gradually restored. If the humidity should be above the percentage required, the valve 11 is maintained closed and the condensing coils function to reduce the humidity.

As the relative humidity varies above or below the desired percentage, the valves 11 and 12 are controlled accordingly. The device is placed directly within the drying compartment, and the moisture derivedin the initial heating of lumber for example,

will directly afi'ectthe hygrostatic element, so that this source of humidity is taken into account and provided for in the present invention.

Any desired type of hygrometer capable of the function noted may be used, and, of course, any type of valves are contemplated. The use of the invention as a system is readily applicable to any and all drying systems where it is desired to directly and automatically control the relative humidity of the drying agent.

It is to benoted that when the steam jets are in operation, as by opening the valve 11, the escape of the water from the condensing coils is cut off, as the valve 12 is closed. Under these circumstances, the water in the coils will rapidly heat up under the heating agent to a non-condensing heat, so that the moisture-reducing function of the coils is interrupted, Without, however, any waste of water. If the system did not provide for such action,there would be required an additional degree of heat to overcome the condensing function of the coils. Therefore the invention tends to an economical use of heat and water, at least to the extent noted.

Having thus described the invention, what is claimed as new, is

1. In a drying kiln, means for adding to the humidity of the air, meansfor taking moisture from the air, and synchronized means including a control element governed by the degree of humidity in the air for controlling'both of said means.

- 2. In a drying kiln, means for adding moisture to the air, means for taking moisture from the air, and synchronized means including a control element governed b the degree of humidity in the air for S1mul-130 taneously controlling and reversely influencing both such means.

3. drying kiln'including a steam jet and a water supplied condenser, valves operatively connected for controlling the steam and water supply to the jet and condenser in relatively reverse order, whereby one of the mediums Will be cut off during the How of the other, and means governed by the moisture in the air for controlling the operation of the valves.

4. A drying kiln including a steam jet and a water supplied condenser, valves operatively connected for controlling the steam and Water supply to the jet and condenser in relatively reverse order, whereby one of the mediums will be cut off during the flow of the other, and a hygrometer for controlling the operation of the valves.

In testimony whereof We affix our signatures.

HERVEY N. ANDREWS.

ROY M. HOLMES. 

